The invention relates to a method for the separate discharge of the individual phase streams of a multiple phase flow consisting, in particular, of a high viscosity, slow-flowing liquid or suspension and a gas flowing at least 100 time faster, the volumetric ratio of the gas to the liquid being greater than 1:1.
Polymers have to be isolated from solutions and/or suspensions in many chemical engineering processes. A known method of concentrating them makes use of a multiple phase flow in a spiral pipe in which a viscous liquid stream is propelled by a flowing gas which can consist of evaporated solvent, with the optional addition of foreign gas, along the wall of the spiral pipe. In this process, the desired evaporation can be achieved by adjusting the evaporation temperature and the partial pressure of the components to be evaporated out in the gas volume, which is controlled by the pressure at the end of the spiral pipe as well as by the optional addition of foreign gas. To separate the individual phase flows, the multiple phase stream is fed into a centrifugal separator.
The disadvantage of the known method lies in the fact that the vapor/gas mixture issuing from the end pipe of the evaporator at high speed is accompanied by liquid residues which are hurled against the housing wall of the centrifugal separator, remain there for a prolonged period and lead to the formation of specks in the case of a certain polymers. The term "specks" refers to highly colored particles of cracked products which are produced from the polymers due to prolonged residence on the wall and simultaneous high temperatures. Discoloration and particles (specks) consequently occur in the product and substantially reduce the quality of the polymers to be isolated.
German Auslegeschrift No. 1 921 045 describes a vertically standing cyclone with a belt screw and a conveyor screw in which the pipe with the multiple phase flow is introduced tangentially with respect to the cyclone. This apparatus has the disadvantage that the simple coil does not clean itself and the formation of specks cannot therefore be reduced, so the quality of the product is again impaired. In addition, the seal of the shaft as it passes through the bottom gives rise to considerable problems in structure and operation.